56
GCDetectors
ASD - AromaticSelectiveDetector
• Heated topermit usewithaGCand semi-volitile
analystes suchasgasolineanddiesel
• Detectsdown to 100ppm
• Conversionof transmittance toabsorbance is
donewith thePeakSimpleSoftware
The SRI Aromatic Selective Detector (ASD) is useful for
the detection of aromatic compounds like benzene and
tolueneeven in thepresenceof interferingmolecules like
gasoline.
TheASD consists of a 15cm long heated tubewith amercury lampmounted at one end and a photodiode
at theother. It canbemountedonanSRIGCor on theseparateModel 110chassiswhich is thenconnected
to any GC. The ASD detects only thosemolecules which absorb the 254nmwavelength produced by the
mercury lamp. AromaticcompoundssuchasBenzeneandTolueneabsorbstronglyat thiswavelengthwhile
aliphatic compounds such asHexane andHeptanedo not.
This chromatogram shows the comparative
response of the PID and ASD to .2μl gasoline.
The PID detects all the gasoline compounds
while theASDdetects only the aromatics.
Notice the comparative chromatograms here
showing the response of the PID and ASD
detectors plumbed in series to an injection of
1000ppm each Heptan and Toluene. The ASD
shows no response to the Heptane but good
response to the Toluene.
8690-0006
ASDdetector
PID
ASD
PID
ASD
